Abstract

Plasma free fatty acid (FFA) kinetics in humans are often measured with only one tracer. In study 1, healthy volunteers received
infusions of [U-13C]linoleate, [U-13C]oleate, and [U-13C]palmitate during continuous feeding with liquid meals low (n = 12) and high (n = 5) in palmitate and containing three labeled fatty acids to measure FFA appearance and fractional spillover of lipoprotein
lipase–generated fatty acids. Study 2 used an intravenous lipid emulsion to increase FFA concentrations during infusion of
linoleate and palmitate tracers. In study 1, there were no differences in spillover of the three fatty acids for the low-palmitate
meal, but linoleate spillover was greater than oleate or palmitate for the high-palmitate meal. In studies 1 and 2, clearance
was significantly greater for linoleate than for the other FFAs. There was a negative correlation between clearance and concentration
for each fatty acid in the two studies. In study 1, concentration and spillover correlated positively for oleate and palmitate
but negatively for linoleate. In conclusion, linoleate spillover is greater than that of other fatty acids under some circumstances.
Linoleate clearance is greater than that of palmitate or oleate, indicating a need for caution when using a single FFA to
infer the behavior of all fatty acids.